Conventional printing systems requiring a fountain solution are difficult to adjust subtle balance between the fountain solution and ink, resulting in emulsifying ink or mixing the fountain solution with ink, which causes unstable ink concentration, scumming, and broke. The no water-planographic original plate, in contrast, has various advantages stemming from requiring no fountain solution.
On the other hand, recent rapid progress in output systems such as prepress systems, image setters, and laser beam printers enables printed images to be converted into digital data. With such progress, systems to prepare printing plates according to novel platemaking processes such as a computer-to-plate process or a computer-to-cylinder process come to be proposed, and new types of printing materials pertinent to these printing systems has been expected and developed. Of these systems, examples of processes for making the no water-planographic printing plates by write with a laser beam include those described in JP-B-42-21879 (The term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-50-158405 (The term "JP-A" as used herein means as an "unexamined published Japanese patent application"), JP-A-5-94008, JP-A-6-55723, JP-A-6-186750, JP-A-7-314934, U.S. Pat. No. 5,353,705, and WO-9401280. For performing printing without using the solution, it is stated in these specifications that an ink-repellent silicone rubber layer is provided on a layer transforming light into heat (hereinafter referred to as a "light-heat transforming layer") which comprising a laser beam-absorbing agent such as carbon black and a self-oxidative binder such as nitrocellulose, or on a metal deposition layer, and that a part of laser beam-irradiated areas of the silicone rubber layer is removed so that the removed areas become ink-receptive.
In this process, the removal of the silicone rubber layer however relies on abrasion of the light-heat transforming layer due to the laser beam irradiation, and therefore, printed images are inferior in linearity of fine lines and roundness of halftone dots, so that improvements therein are fully expected. Further, inherently poor adhesion between the light-heat transforming layer and the silicone rubber layer often causes the printing plate to suffer damage on handling or during printing, and the damaged areas are inked to form undesired images in these portions, which is a fatal drawback to the printing plate. Although it is described in some specifications that a silane coupling agent is added to the silicone rubber layer to compensate for this drawback, this is insufficient to increase the adhesion of the light-heat transforming layer with the silicone rubber layer, and also has little effect on improvement in resistance to scratching.